Fe2O4 Composites Research Articles

Electromagnetic interference shielding properties of PMMA modified-Co0.5Zn0.5Fe2O4 − polyaniline composites

Present work reports solution combustion synthesis (SCS) of Co0.5Zn0.5Fe2O4 spinel ferrite, its chemical modification with polymethylmethacrylate (PMMA), synthesis of polyaniline (PANI), and electromagnetic interference (EMI) shielding properties of their composites. Both as-prepared and PMMA-modified Co0.5Zn0.5Fe2O4 adopt cubic spinel structure as shown by X-ray diffraction studies. Field emission scanning electron microscopy images show the agglomerated and microporous nature of the ferrites. High resolution transmission electron microscopy image of as-prepared Co0.5Zn0.5Fe2O4 shows lattice fringes related to (311) plane of the spinel structure. X-ray photoelectron spectroscopy studies reveal the presence of Co2+, Zn2+, and Fe3+ in tetrahedral and octahedral coordinations in the ferrite. EMI shielding properties are evaluated for PMMA-modified Co0.5Zn0.5Fe2O4 and PANI composites in different weight ratios. Composites containing PMMA-modified ferrite and PANI with 50:50 and 10:90 weight ratios show the best performance among all the composites in 2−20 GHz frequency range. Optimized PMMA-modified Co0.5Zn0.5Fe2O4 and PANI composite with the ratio of 10:90 shows shielding effectiveness (SE) values of −16.6 to −24.2 dB in 2−20 GHz frequency region.Graphical

Enhancing electromagnetic wave absorption performance through construction of three-dimensional multilayered SiCw/Y3Si2C2/Ni0.5Zn0.5Fe2O4 composites

In this study, three-dimensional (3D) multilayer electromagnetic wave absorbing (EMWA) materials SiCw/Y3Si2C2/Ni0.5Zn0.5Fe2O4 were fabricated for the first time. A two-dimensional (2D) Y3Si2C2 coating was synthesized onto the one-dimensional (1D) SiCw surface by the molten salt method. Subsequently, one layer of zero-dimensional (0D) Ni0.5Zn0.5Fe2O4 nanoparticles was deposited onto the Y3Si2C2 coating surface via hydrothermal reaction. The microstructure and electromagnetic wave absorption mechanism of SiCw/Y3Si2C2/Ni0.5Zn0.5Fe2O4 were systematically investigated. The introduction of 2D Y3Si2C2 and 0D Ni0.5Zn0.5Fe2O4 enhanced impedance matching and provided abundant heterogeneous interfaces, thus leading to interface polarization loss. Owing to the promoted impedance matching and superb attenuation capacity, 3D multilayered SiCw/Y3Si2C2/Ni0.5Zn0.5Fe2O4 composites exhibit superior EMWA performance in comparison with origin SiCw. For the SiCw/Y3Si2C2/Ni0.5Zn0.5Fe2O4 composites, their minimum reflection loss (RLmin) can be achieved −43.95 dB and the effective absorption bandwidth (EAB) is 4.08 GHz when the thickness is 2.12 mm. This study could pave a reference for the investigation of multi-dimensional hybrid structure EMWA material.

Relationship between the Synthesis Method and the Magnetoelectric Properties of Bismuth Sodium-Potassium Titanate/Nickel Cobalt Ferrite Lead-Free Composites

In this work, the influence of the synthesis methods of piezoelectric and magnetostrictive phases on the final properties of the Bi0.5(Na0.8K0.2)0.5TiO3-Ni0.5Co0.5Fe2O4 composites was studied. Different routes were used to individually synthesize each phase, and the composites were prepared using different fractions for each phase. Composites were sintered, and the structural, microstructural, dielectric, and magnetoelectric properties were evaluated. According to the selected synthesis method employed for each phase, different particle sizes and reactivities of the individual phases were obtained. These differences determined the suitable sintering temperature for each set of composites and were responsible for the final properties. In fact, magnetoelectric properties were modulated by the combination of composition and synthesis routes.

In-situ synthesis of NiCo/(Ni,Co)O/(Ni,Co)Fe2O4 composite as high-performance microwave absorber

NiCo/(Ni,Co)O/(Ni,Co)Fe2O4 composites were in-situ prepared by solution combustion method using metal nitrates as oxidant and glycine as organic fuel. The amounts of various intermetallic and oxide phases were controlled by amounts of metal precursor. The magnetic properties proved the presence of Ni1-xCox phase instead of pure Ni and Co phases. The combusted composites showed spongy microstructure without any special morphology for various phases. The (Ni,Co)O-49 wt % NiCo composite powders had the effective absorption bandwidth (EAB) of 3.6 GHz at a matching thickness (1.8 mm) in Ku band. By using the ferric precursor, the (Co,Ni)O-30 wt %NiCo-15 wt % (Co,Ni)Fe2O4 composite exhibited a rather broader EAB of 3.9 GHz at a smaller matching thickness of 1.2 mm in Ku band.

3D hierarchical porous structure formed by CS/GP/Ni0.5Co0.5Fe2O4 for high-efficiency microwave absorption

Preparation of light and efficient microwave absorbing materials is considered as a good solution to electromagnetic wave pollution. It is expected to achieve high-performance absorbing materials by combining light carbon-based materials with high reflection loss (RL) ferrite materials. Herein, corn stalk (CS)/ grapefruit peel (GP)/Ni0.5Co0.5Fe2O4 composites were prepared by a simple solvothermal method. By adjusting the ratio of CS/GP, a 3D hierarchically porous structure composed of 0D Ni0.5Co0.5Fe2O4, 1D CS and 2D GP was gained. This unique structure can effectively improve the conductive loss and multiple polarization intensity. Meanwhile, it contributes to the dielectric-magnetic combination, which leads to impedance matching. The minimum reflection loss reaches −43.95 dB and the corresponding effective absorption bandwidth is up to 4.81 GHz with 3 mm thickness. It provides a valuable way to realize light and efficient electromagnetic wave absorption.

Magnetodielectric response of composites based on a natural garnet and spinel ferrites for sub-GHz wireless applications

A natural garnet with excellent dielectric properties was mixed with different weight percentages of two spinel ferrites, Ni0.5Zn0.5Fe2O4 (NZO) and LiFe5O8 (LFO) to tailor its magnetodilectric properties. 3 wt% B2O3 was added to enhance the density of the composites. X-ray diffraction study revealed the decomposition of the mineral into hematite and cordierite and vibrational spectroscopic analysis confirmed the non-reactivity of decomposed mineral with spinel ferrites. Microstructural analysis shows well densified and almost tightly packed grains for garnet-Ni0.5Zn0.5Fe2O4 (G-N) and garnet-LiFe5O8 (G-L) composites. The optimised dielectric and magnetic properties of 0.5 G-0.5 NZO are εr = 4.1, μr = 1.8, tan δε = 0.02, tan δμ = 0.49, whereas that of 0.5 G–0.5 LFO are εr = 4.4, μr = 1.4, tan δε = 0.001, tan δμ = 0.05 at 1 GHz. Due to the moderate permittivity of garnet, a better impedance matching compared to magnetodielectric composites based on high-permittivity dielectric counterparts is observed. Hence, the present study indicates that G-N and G-L composites are potential candidates for sub-gigahertz wireless applications.

Synthesis and characterization of Mg\u2013Zn ferrite based flexible microwave composites and its application as SNG metamaterial

In this article, we propose SNG (single negative) metamaterial fabricated on Mg–Zn ferrite-based flexible microwave composites. Firstly, the flexible composites are synthesized by the sol-gel method having four different molecular compositions of MgxZn(1−x)Fe2O4, which are denoted as Mg20, Mg40, Mg60, and Mg80. The structural, morphological, and microwave properties of the synthesized flexible composites are analyzed using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and conventional dielectric assessment kit (DAK) to justify their possible application as dielectric substrate at microwave frequency regime. Thus the average grain size is found from 20 to 24 nm, and the dielectric constants are 6.01, 5.10, 4.19, and 3.28, as well as loss tangents, are 0.002, 0.004, 0.006, and 0.008 for the prepared Mg–Zn ferrites, i.e., Mg20, Mg40, Mg60, and Mg80 respectively. Besides, the prepared low-cost Mg–Zn ferrite composites exhibit high flexibility and lightweight, which makes them a potential candidate as a metamaterial substrate. Furthermore, a single negative (SNG) metamaterial unit cell is fabricated on the prepared, flexible microwave composites, and their essential electromagnetic behaviors are observed. Very good effective medium ratios (EMR) vales are obtained from 14.65 to 18.47, which ensure the compactness of the fabricated prototypes with a physical dimension of 8 × 6.5 mm2. Also, the proposed materials have shown better performances comparing with conventional FR4 and RO4533 materials, and they have covered S-, C-, X-, Ku-, and K-band of microwave frequency region. Thus, the prepared, flexible SNG metamaterials on MgxZn(1−x)Fe2O4 composites are suitable for microwave and flexible technologies.

Studies on Exchange-Coupled Magnetodielectric Ceramics for Microwave Absorption in Ku-Band

Series of exchange-coupled BaFe12O19 (BaM)/CoFe2O4 (CFO) and BaM/Co0.5Zn0.5Fe2O4 (CZFO) composites were synthesized using the autocombustion method. Effect of soft (CFO/CZFO) phase weight fraction on structural, magnetic, and microwave properties of composites has been investigated and compared. X-ray diffraction patterns and scanning electron microscope (SEM) micrographs confirmed the presence of BaM and CFO/CZFO phases with well-distinguished grains in the composites. Existence of interfacial coupling was verified by smooth demagnetization behavior and single peak in corresponding $\text{d}M/\text{d}H$ curves. Saturation magnetization ( $M_{s}$ ) and coercivity showed strong dependence on exchange interactions between hard and soft magnetic spins. Compared to BaM, $M_{s}$ of composites were 22% and 36% higher with CFO and CZFO, respectively. Frequency-dependent complex permittivity ( $\varepsilon$ ) and permeability ( $\mu $ ) in ${\text{K}}_{u}$ -band were found to be dependent upon the relative composition and nature of soft phase. Maximum $\varepsilon $ of 45 and $\mu $ of 1.6 were achieved for BaM/CFO (50/50) composite. Exchange-coupled magnetodielectric with high $\varepsilon $ and $\mu $ were developed for various microwave applications.

Enhanced dielectric, ferroelectric, and ferromagnetic responses of BaZr0.2Ti0.8O3–Ni0.5Zn0.5Fe2O4 multiferroic ceramic composite

Pure BaZr0.2Ti0.8O3, pure Ni0.5Zn0.5Fe2O4, and 80BaZr0.2Ti0.8O3–20Ni0.5Zn0.5Fe2O4, 70BaZr0.2Ti0.8O3–30Ni0.5Zn0.5Fe2O4, and 60BaZr0.2Ti0.8O3–40Ni0.5Zn0.5Fe2O4 multiferroic composites were prepared by a solid-state sintering method, and their structural, morphological, electrical (dielectric and ferroelectric), and magnetic properties were analyzed. A perovskite tetragonal phase (BaZr0.2Ti0.8O3) and a cubic spinel phase (Ni0.5Zn0.5Fe2O4) were simultaneously present in each composite. Peak shifting toward higher angles was observed for the 80BaZr0.2Ti0.8O3–20Ni0.5Zn0.5Fe2O4 and 70BaZr0.2Ti0.8O3–30Ni0.5Zn0.5Fe2O4 composites. BaZr0.2Ti0.8O3 part of all the composites demonstrated tensile strain value, while Ni0.5Zn0.5Fe2O4 part exhibited compressive strain values. A grain growth reduction phenomenon was observed with increasing Ni0.5Zn0.5Fe2O4 content in the composites. The largest average grain size was obtained for 80BaZr0.2Ti0.8O3–20Ni0.5Zn0.5Fe2O4 (933.23 ​nm), while the values for 70BaZr0.2Ti0.8O3–30Ni0.5Zn0.5Fe2O4 and 60BaZr0.2Ti0.8O3–40Ni0.5Zn0.5Fe2O4 composites were 843.07 ​nm, 718.35 ​nm, respectively. All composites exhibited giant dielectric constants because of the electron hopping phenomenon between ​Fe2+and ​Fe3+. The 60BaZr0.2Ti0.8O3–40Ni0.5Zn0.5Fe2O4 composite exhibited the highest dielectric constant of 88217.31 ​at 100 ​Hz. Similarly, it showed an enhanced dielectric loss of 2.77 (at 100 ​Hz). The 80BaZr0.2Ti0.8O3–20Ni0.5Zn0.5Fe2O4 composite exhibited the highest remnant polarization (13.58 ​μC ​cm−2), charge density (0.28 ​J ​cm−3), and discharge density (0.20 ​J ​cm−3) among the synthesized composites. However, 70BaZr0.2Ti0.8O3–30Ni0.5Zn0.5Fe2O4 exhibited the largest energy storage efficiency of 75%. Although pure BaZr0.2Ti0.8O3 did not show any response to an applied magnetic field, meaningful hysteresis loops were obtained for pure Ni0.5Zn0.5Fe2O4 and the (1-x)BaZr0.2Ti0.8O3-xNi0.5Zn0.5Fe2O4 composites. In addition, 60BaZr0.2Ti0.8O3–40Ni0.5Zn0.5Fe2O4 showed the highest saturation magnetization (17.52 emu/g) and remnant magnetization (0.92 emu/g) among the synthesized composites. Eventually, (1-x)BaZr0.2Ti0.8O3-xNi0.5Zn0.5Fe2O4 composites showed better performance compared to pure BaZr0.2Ti0.8O3 and Ni0.5Zn0.5Fe2O4 ceramics.

Effect of Polyaniline on Magnetic and Microwave Absorption Properties in SrFe12O19/Zn0.4Co0.2Ni0.4Fe2O4 Ferrite Nanocomposites

Polyaniline PANI/(SrFe12O19)(1-x)/(Co0.8Ni0.2Fe2O4)(x) (x = 0.2, 0.4, 0.6, 0.8) composites were prepared via the in situ polymerization process. The structure, morphology and electromagnetic absorption properties of samples were studied. XRD (x-ray diffractometer), FESEM (field emission scanning electron microscopy), and FTIR (field transform infrared) analyses demonstrated that SrFe12O19/Zn0.4Co0.2Ni0.4Fe2O4 ferrite particles were covered by PANI coating. VSM measurement revealed by adding non-magnetic polymer (PANI), magnetic features of aimed composites declined. The electromagnetic absorption of synthesized samples was measured by VNA. In the frequency range of 8.2–12.4 GHz (X-Band), the reflection loss improved to − 28.5 dB from − 2.93 dB composites of PANI/(SrFe12O19)0.2/(Zn0.4Co0.2Ni0.4Fe2O4)0.8 in comparison to (SrFe12O19)0.2/(Zn0.4Co0.2Ni0.4Fe2O4)0.8. Due to the perfect impedance matching between PANI as the dielectric part, and ferrites in the case of the magnetic part, the reflection loss decreased in PANI/(SrFe12O19)(1-x)/(Co0.8Ni0.2Fe2O4)(x) composites. The minimum reflection loss of the PANI/SrFe12O19/Zn0.4Co0.2Ni0.4Fe2O4 composites was − 28.6 dB at the frequency of 11.5 GHz.

Structural, dielectric and magnetic studies on polyaniline-decorated Ni0.5Cu0.5Fe2O4 nanoferrites for electromagnetic interference shielding applications

With the aim of developing effective electromagnetic interference (EMI) shielding materials, polyaniline-decorated Ni0.5Cu0.5Fe2O4 nanoferrites were synthesized via in situ polymerization method. Synthesized samples were characterized using different techniques such as X-ray diffraction analysis, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. Thermal behavior of polyaniline (PAni)/Ni0.5Cu0.5Fe2O4 composites is studied in the temperature range 25–700 °C. Present Ni0.5Cu0.5Fe2O4 nanoparticles and PAni/Ni0.5Cu0.5Fe2O4 composites exhibited hysteretic behavior in the studied magnetic field range. Values of saturation magnetization and coercivity for Ni0.5Cu0.5Fe2O4 nanoparticles decrease with coating of polyaniline due to increase in particle–particle separation which reduces the inter-particle interaction. Maximum EMI shielding effectiveness (SE) values obtained for Ni0.5Cu0.5Fe2O4 nanoparticles and PAni/Ni0.5Cu0.5Fe2O4 composites are 11.54 dB and 66.56 dB, respectively. Secured higher SE values shows that the composites possess great potential in EMI shielding applications.

Enhanced Microwave Absorption of Reduced Graphene Oxide/Ni0.4Zn0.4Co0.2Fe2O4 Composite at Ultrathin Thickness

Reduced graphene oxide (rGO)-anchored Ni0.4Zn0.4Co0.2Fe2O4 (NZCF) composites were successfully synthesized by a hydrothermal process and then mixed with paraffin wax. The phase composition and microstructure were investigated by Fourier transform infrared (FT-IR) spectroscopy, x-ray diffraction, and scanning electron microscopy. The results confirmed that the rGO particles covered the modified ferrite grains, and the NZCF particles exhibited a typical spinel structure with the characteristic of the Fd3m cubic groups. In addition, the electromagnetic parameters were measured via a vector network analyzer. The composites with paraffin wax exhibited excellent electromagnetic wave absorption performance, comparable or superior to that of most reported absorbers. The reflection loss was excellent, with a value of −47.10 dB with ultralow thickness of only 0.44 mm obtained from the rGO/NZCF composite with paraffin volume fraction of 20%, and the maximum bandwidth reached 3.7 GHz with merely 1.5 mm in thickness. Therefore, the rGO/Ni0.4Zn0.4Co0.2Fe2O4 composites are potential candidates for electromagnetic wave absorption applications.

Synthesis and enhanced microwave absorption performance of CIP@ SiO2@Mn0.6Zn0.4Fe2O4 ferrite composites

Novel core@shell@shell structured carbonyl iron powder (CIP)@SiO2@ Mn0.6Zn0.4Fe2O4 ferrite composites having great microwave absorption characteristics were successfully synthesized using chemical co-precipitation. The microstructure, morphology and microwave absorption performance of CIP@SiO2@Mn0.6Zn0.4Fe2O4 ferrite composites were systematically investigated. The results show that both coating layers of SiO2 and Mn0.6Zn0.4Fe2O4 are uniform and fine. The prepared CIP@SiO2@Mn0.6Zn0.4Fe2O4 composites in this study display better dielectric loss and frequency characteristic at high frequency than CIP, CIP@SiO2 and CIP@Mn0.6Zn0.4Fe2O4. The results of electromagnetic parameters also indicate that the enhanced microwave absorption performance primarily originates from the substantial contributions of magnetic loss to reflection loss. The optimal value of reflection loss of CIP@SiO2@Mn0.6Zn0.4Fe2O4 having the thickness of 2 mm can reach up to −44.24 dB at 11.57 GHz as well as the bandwidth (RL ≤ −10 dB) from 9.04 to 16.16 GHz among the frequency range from 2 to 18 GHz. In addition, the greatly enhanced microwave absorption performance is attributed to good wave impedance matching, high attenuation constant, multi-relaxation processes and multiple interfacial polarization.

Synthesis and enhanced magnetoelectric properties of [formula omitted] composites

Magnetoelectric (ME) (1−x)Pb(Zr0.52Ti0.48)O3+(x)Co0.9Mn0.1Fe2O4 composites were prepared by mixed oxide route. XRD analysis revealed development of two-phase composites with distinct ferroelectric (Pb(Zr0.52Ti0.48)O3) and ferrite (Co0.9Mn0.1Fe2O4) phases. However, Rietveld refinement confirmed the coexistence of tetragonal and rhombohedral perovskite structures for Pb(Zr0.52Ti0.48)O3 phase while cubic spinel structure for Co0.9Mn0.1Fe2O4 phase. Impedance spectroscopy was employed to investigate the effect of constituent phases on the conduction mechanism, dielectric relaxation and resistive properties of prepared composites. It was found that small amount of Mn substituted in CoFe2O4 not only improved the resistive properties of ferrite phase but also enhanced the ME coupling coefficient ‘αE’ in the prepared composites. The obtained value of αE was found to be two orders of magnitude higher in comparison to the Pb(Zr0.52Ti0.48)O3−CoFe2O4 composites with similar wt% compositions. The observed enhancement in αE is explained in terms of dense microstructure, better phase connectivity and increased resistivity of ferrite phase.

Synthesis and enhanced microwave absorption properties of urchin-like polyaniline/Ni0.4Zn0.4Co0.2Fe2O4 composites

A novel polyaniline/Ni0.4Zn0.4Co0.2Fe2O4 (PANI/NZCF) composite was synthesized by in situ polymerization of aniline in the presence of NZCF. The studies of structural, morphological and surface chemical bonding states were performed by X-ray diffraction, scanning electron microscopy and Fourier transform-infrared spectrometry, respectively. It was found that greater reflection loss and wider absorption bandwidths were possible by adjusting the mass ratio of NZCF to PANI on account of electromagnetic loss and impedance matching. The highest reflection loss (RL) was − 40 dB at the frequency 15.8 GHz for the PANI/NZCF composite when the effective absorption frequency at which RL < − 10 dB was in the range of 13.5–18 GHz with an absorber thickness of 1.7 mm at the mass ratio of 2:1. These effects are due to the urchin-like structure when compared to traditional encapsulation structures. Therefore, the above findings show that the PANI/NZCF composite with negligible thickness and strong absorption properties has great potential in the application of electromagnetic shielding and microwave absorbing.

Influence of the Preparation Conditions and Percolation Threshold on the Properties of Lead Zirconate Titanate/Cobalt Nickel Ferrite Magnetoelectric Composites

We have prepared magnetoelectric (ME) composite ceramics, free of foreign phases, in the lead zirconate titanate–cobalt nickel ferrite two-phase system: xPZT-36 + (100–x)Ni0.9Co0.1Fe2O4. The sol–gel derived ferrite powder used in our preparations seems to be doped with titanium cations from the PZT-36. The ceramics have a percolation threshold at x = 50–70 wt %, which is due to the increased electrical conductivity of Ni0.9Co0.1Fe2O4. As a consequence, the piezoelectric parameters of the ME ceramics drop sharply at x < 50–70 wt %: the piezoelectric moduli |dij| and piezoelectric voltage coefficients |gij| decrease by a factor of 3–5 in this composite range. The piezoelectric parameters |dij| and |gij| of the composites produced using the fine ferrite powder exceed those of the materials prepared using macrocrystalline Ni0.9Co0.1Fe2O4 powder by more than a factor of 2. The piezoelectric voltage coefficient g33 correlates with the ME coefficient ΔE/ΔH. The highest ME conversion efficiency (up to 45 mV/(cm Oe)) is offered by the 80 wt % PZT-36 + 20 wt % Ni0.9Co0.1Fe2O4 composites, whose composition lies in a subpercolation region. Even though the composites produced using the fine ferrite powder possess improved piezoelectric properties, they have smaller ΔE/ΔH coefficients (no greater than 25 mV/(cm Oe)), which can be tentatively attributed to the degradation of the properties of the ferrite as a consequence of doping with Ti4+ cations during the sintering of the composite ceramics.

Structural, magnetic and microwave absorption properties of SrFe12O19/Ni0.6Zn0.4Fe2O4 composites prepared by one-pot solution combustion method

SrFe12O19/Ni0.6Zn0.4Fe2O4 composites were synthesized by one-pot solution combustion method. The effects of NiZn ferrite content on phase, structure, microstructure and magnetic properties of composites were investigated by X-ray diffractometry, infrared spectroscopy, electron microscopy and vibrating sample magnetometry techniques. Strontium hexaferrite and NiZn ferrite phases were well crystallized following calcination at 900 °C without any impurities being formed. The composites were composed of platelet-like SrFe12O19 particles being mixed with quasi-spherical NiZn ferrite particles. The composites containing 10 wt% Ni0.6Zn0.4Fe2O4 exhibited a single magnetization curve with maximum saturation magnetization of 56 emu/g, as a confirmation of exchange coupling, while other composites had “bee waist” type hysteresis loop. The coercivity of composites decreased from 5143 to 1778 Oe with addition of NiZn ferrite phase. The microwave absorption measurements in X-band (8–12 GHz) showed a maximum absorption of −23.5 dB at 9.9 GHz for SrFe12O19-10 wt% Ni0.6Zn0.4Fe2O4 composite in comparison with the other composites.

Activated carbon/Mn0.6Zn0.4Fe2O4 composites: Facile synthesis, magnetic performance and their potential application for the removal of methylene blue from water

Activated carbon/Mn0.6Zn0.4Fe2O4 (AC/MZF) composites were synthesized by a facile bonding method and were used as adsorbents for the removal of methylene blue (MB) dye from water. The structure, morphology and magnetic properties of the as-prepared composites were characterized by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy and with a vibrating sample magnetometer. The results indicated that Mn0.6Zn0.4Fe2O4 particles were bonded with the activated carbon in the composite. The composite adsorbents exhibited a clear hysteretic behavior under an applied magnetic field, which allowed their magnetic separation from water. Batch experiments were carried out to investigate the adsorption isotherms and kinetics of MB on the composite. The experimental data fitted well with the Freundlich model. The 1/n (where n is the Freundlich constant) values of MB adsorption by AC/MZF were in the range of 0.1024–0.1419, showing that the adsorption process was favorable. The adsorption kinetics were found to follow the pseudo-second-order kinetic model. The mean free energy evaluated through the Dubinin–Radushkevich model was below 8kJmol−1, which indicates physisorption. Additionally, it was found that the adsorption of MB on AC/MZF was a spontaneous endothermic physical process according to thermodynamic calculations. AC/MZF could be recovered well using 3wt.% H2O2, and its adsorption capacity could preserve an excellent level of 274.0mgg−1 after five runs. It was indicated that the as-prepared composites could be used as promising and effective adsorbents for the removal of MB from water.

Synthesis of low core loss Finemet/Ni0.5Zn0.5Fe2O4 composites by co-precipitation method

Finemet/Ni0.5Zn0.5Fe2O4 core/shell structure composites have been prepared by a co-precipitation method followed by a high temperature sintering process. The formation mechanism of the core/shell structures and the effects of oxygen partial pressure during the sintering process on the phase structure, microstructure, and magnetic properties were discussed. Low and high oxygen partial pressures resulted in the formation of crystal defects and a reduction of the magnetic properties of the composites. The magnetic properties could be adjusted by controlling the oxygen partial pressure and the optimal magnetic properties of the composites were obtained by sintering under an oxygen partial pressure of 10%. The resulting composite exhibited a high permeability of 61, a high saturation magnetization of 135.5 emu/g and a low core loss of approximately 30.5 mW/cm3 at 100 kHz and 100 mT.

Size-dependent magnetoelectric response of (Bi0.5Na0.5TiO3-Bi0.5K0.5TiO3)-(Ni0.8Zn0.2)Fe2O4 particulate composites

In this paper, we investigated the effect of magnetic grain size on magnetoelectric responses of particulate magnetoelectric 0.7(Bi0.5Na0.5TiO3-Bi0.5K0.5TiO3)-0.3(Ni0.8Zn0.2)Fe2O4 (BNKT-NZFO) composites. The coexistence of two chemically separated phases was confirmed using x-ray diffraction analysis. The composites had homogeneous microstructure with controlled grain size. The magnetoelectric response of the BNKT-NZFO composites sensitively depended on the grain size of the NZFO phase and the magnetoelectric voltage coefficients presented a marked enhancement of 33% in the engineered grain size range. This result indicated that tailoring the magnetic grain size physically will provide a powerful mean of enhancing magnetoelectric coupling in a two-phase particulate composite, with large potential application in area of magnetic field sensor.